JP2009275063A - Frictional material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a frictional material which maintains a necessary friction coefficient, prevents the grinding of a counter material on a frictional braking, and can prevent the generation of vibrations due to the deformation of the counter material, the staining of a wheel with the worn powder of the counter material, and the like. <P>SOLUTION: Provided is the frictional material characterized by substantially not containing a hard substance having a Mohs' scale of >6 and containing a laminar clay mineral into the interlaminar layers of which titania particles are inserted, in an amount of 0.5 to 20 mass%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a friction material. More specifically, the present invention maintains a necessary coefficient of friction and suppresses grinding of the mating material during friction braking, generates vibration due to deformation of the mating material, dirt on the wheel due to wear powder of the mating material, and the like. It is related with the friction material which can prevent.

  Non-asbestos brake friction materials used for brake pads of automobiles, etc., for example, a base material made of metal fibers such as steel and copper, ceramics, inorganic fibers such as carbon, organic fibers such as aramid fibers, graphite, Lubricants such as antimony trisulfide and molybdenum disulfide, fillers such as swellable clay minerals, barium sulfate, calcium carbonate and calcium hydroxide, and oxide ceramic powders such as cashew dust, silica, alumina and zirconia, metal powders It is produced by blending a friction modifier such as a binder resin (binding material) such as a phenol resin or an epoxy resin with these components, sufficiently stirring and mixing, and then performing compression molding while heating. .

  However, in the case of a friction material containing a hard substance such as the oxide-based ceramic powder, the counterpart material is ground during friction braking, and as a result, vibration occurs due to deformation of the ground counterpart material and the wheel due to wear powder of the counterpart material. May cause problems such as dirt.

Therefore, in order to solve such a problem, for example, in Patent Document 1, an elastomer is included in the friction material to improve at low speed and low load. Since the load on the brake is high, further improvement is desired.
JP 2005-336340 A

  Under such circumstances, the present invention maintains a necessary coefficient of friction and suppresses grinding of the mating member during friction braking, generates vibration due to deformation of the mating material, and wears the wheel due to wear powder of the mating material. An object of the present invention is to provide a friction material capable of preventing dirt and the like.

  As a result of intensive studies to develop a friction material having the above-mentioned preferable properties, the present inventors have found that a hard material having a Mohs hardness of more than 6 is substantially not contained and a layered clay mineral having a specific structure is contained at a predetermined ratio. The inventors have found that the purpose can be achieved by the friction material to be included, and have completed the present invention based on this finding.

That is, the present invention
(1) A friction material characterized in that it contains substantially no hard substance with a Mohs hardness of more than 6 and contains 0.5 to 20% by mass of a layered clay mineral formed by inserting titania particles between the layers,
(2) The friction material according to (1) above, wherein the average particle diameter of titania particles in the layered clay mineral formed by inserting titania particles between layers is 3 to 200 nm,
(3) The friction material according to (1) or (2) above, wherein the content of titania particles in the layered clay mineral obtained by inserting titania particles between the layers is 10 to 80% by mass, and (4) the interlayer The layered clay mineral formed by inserting titania particles into the layered clay mineral obtained by calcining a layered clay mineral intercalated with a titania precursor formed by a sol-gel method at a temperature of 500 ° C. or higher (1 ) To (3), friction material according to any one of items
Is to provide.

  According to the present invention, while maintaining a necessary friction coefficient, it is possible to suppress grinding of the counterpart material during friction braking, and to prevent generation of vibration due to deformation of the counterpart material and contamination of the wheel due to wear powder of the counterpart material. The friction material which can be provided can be provided.

  The friction material of the present invention is substantially free of a hard substance having a Mohs hardness of more than 6, and contains a layered clay mineral formed by inserting titania particles between layers in a proportion of 0.5 to 20% by mass. .

  In the friction material of the present invention, “substantially does not contain a hard substance having a Mohs hardness of more than 6” means that a hard substance having a Mohs hardness of more than 6 that is inevitably mixed can be tolerated. The content of hard substance having a hardness exceeding 6 is about 0 to 0.5% by mass.

  Examples of the hard substance having a Mohs hardness of more than 6 include silica (7), alumina (9), zirconia (7), dichromium trioxide (8), and the like. The numerical values in parentheses indicate the Mohs hardness. It is preferable that the Mohs hardness of the hard substance substantially not contained is 7 or more.

  If the friction material is substantially free of a hard material having a Mohs hardness of more than 6 as described above, grinding of the mating material during friction braking is suppressed, and vibration due to deformation of the mating material or wheel wear due to the wear powder of the mating material is suppressed. Dirt can be prevented.

  The Mohs hardness is a method using the ten kinds of standard minerals selected below and scratching them in order from the lower hardness, and setting the hardness before the damaged mineral as the Mohs hardness of the substance. Standard minerals are in ascending order of hardness. Talc Gypsum 3. Calcite 4. Fluorite 5. Apatite 6. Elite feldspar Crystal 8 Yellow ball 9. Steel balls 10. It is a diamond.

  In the friction material of the present invention, titania particles are inserted between layers in order to suppress a decrease in the friction coefficient due to the fact that it does not substantially contain a hard substance having a Mohs hardness of more than 6, and to maintain the necessary friction coefficient. A layered clay mineral (hereinafter sometimes abbreviated as titania particle-inserted clay mineral) is contained.

[Titania particle-inserted clay mineral]
Although there is no particular limitation on the method for producing the titania particle-inserted clay mineral contained in the friction material of the present invention, for example, a layered clay mineral obtained by intercalating a titania precursor formed by a sol-gel method between layers at a temperature of 500 ° C or higher. It can obtain by baking with.

1. Layered clay mineral The layered clay mineral used as one of the raw materials of the titania particle-inserted clay mineral in the present invention is a phyllosilicate having a layered structure, and includes natural and clay minerals and synthetic clay minerals having a cation exchange capacity. Can be mentioned. Specific examples include kaolinite, smectite, vermiculite, mica, brittle mica, and chlorite. Examples of the smectite include montmorillonite, saponite, piderite, and nontronite. In addition, synthetic fluorine mica obtained by fluorinating mica can be used. This synthetic fluorine mica is suitable as a layered clay mineral because of small variations in quality, and examples of the synthetic fluorine mica include sodium tetrasilicate fluorine mica (NaMg _2.5 Si ₄ O ₁₀ F ₂ ). it can.
In this invention, these layered clay minerals may be used individually by 1 type, and may be used in combination of 2 or more type.

2. Production of titania particle-inserted clay mineral The titania particle-inserted clay mineral includes, for example, (a) a step of intercalating a titania precursor formed by a sol-gel method between layers of the layered clay mineral in an aqueous medium, and (b) ) After the step (a), the solid obtained by solid-liquid separation is washed with water, and then subjected to a firing treatment at a temperature of 500 ° C. or higher.

2-1. Step (a) This step (a) is a step of intercalating a titania precursor formed by the sol-gel method between the layers of the layered clay mineral described above in an aqueous medium.
In the step (a), as a method of intercalating the titania precursor formed by the sol-gel method between the layers of the layered clay mineral, for example, the following method can be employed.

  First, an aqueous medium and a lamellar clay mineral are mixed, and sufficient interstitial water is taken into the clay mineral to form a sol in which the layer gap is maximized.

  On the other hand, a hydrolyzable titanium compound is added to an organic acid aqueous solution having an appropriate concentration, and the titanium compound is hydrolyzed and condensed at a temperature of about 20 to 70 ° C. for about 5 to 240 minutes to obtain a titania precursor sol. Let it form. In this case, the organic acid used is for stabilizing the titania precursor sol, and examples thereof include carboxylic acids such as acetic acid, oxalic acid, and formic acid.

  Next, the layered clay mineral sol and the titania precursor sol are mixed and kept at a temperature of about room temperature to about 100 ° C. for about 10 to 300 minutes, thereby allowing the interlayer water and the titania incorporated into the clay mineral. The precursor sol is replaced, and the titania precursor is sandwiched between layers of clay mineral and intercalated.

<Hydrolyzable titanium compound>
Examples of the hydrolyzable titanium compound used for the formation of the titania precursor sol include, for example, the general formula (1)
R ³ _n TiX _4-n (1)
(In the formula, R ³ represents a non-hydrolyzable group, X represents a hydrolyzable group or a hydroxyl group, and n is an integer of 0 to ^{3. When} there are a plurality of R ^{3 s} , the plurality of R ^{3 s} are the same. However, they may be different, and when there are a plurality of X, the plurality of X may be the same or different.
The compound represented by these can be used.

In the general formula (1), examples of the non-hydrolyzable group represented by R ³ include a hydrocarbon group which may have a functional group. Examples of the hydrocarbon group include linear or branched alkyl or alkenyl groups, cycloalkyl groups, aryl groups, and aralkyl groups.

  The alkyl group and alkenyl group preferably have 1 to 25 carbon atoms, particularly 1 to 3 carbon atoms, and the cycloalkyl group preferably has 3 to 25 carbon atoms, particularly 3 to 6 carbon atoms. The aryl group preferably has 6 to 25 carbon atoms, particularly 6 to 10 carbon atoms, and the aralkyl group preferably has 7 to 25 carbon atoms, particularly 7 to 10 carbon atoms.

  Examples of the functional group that may be introduced into the hydrocarbon group include an ester bond, an ether bond, an epoxy group, an amino group, a carboxy group, a carbonyl group, an amide group, a mercapto group, a sulfonyl group, a sulfenyl group, and a cyano group. , Hydroxyl group, halogen atom and the like.

  In the general formula (1), examples of the hydrolyzable group in X include an alkoxy group, an alkenyloxy group, a ketoxime group, an acyloxy group, and a halogen atom. n is an integer of 0 to 3, preferably an integer of 0 to 2, and more preferably 0 or 1.

  Preferred examples of the hydrolyzable titanium compound represented by the general formula (1) include tetraethoxy titanium, tetra-n-propoxy titanium, tetraisopropoxy titanium, tetra-n-butoxy titanium, tetraisobutoxy titanium, Tetra-sec-butoxy titanium, tetra-tert-butoxy titanium, tetraacetoxy titanium, methyl triethoxy titanium, vinyl triethoxy titanium, phenyl triethoxy titanium, methyl tri-n-propoxy titanium, vinyl tri-n-propoxy titanium, methyl triiso Examples include propoxy titanium, vinyl triisopropoxy titanium, and phenyl triisopropoxy titanium. These hydrolyzable titanium compounds may be used individually by 1 type, and may be used in combination of 2 or more type.

2-2. (B) Step After the step (a), the step (b) is subjected to solid-liquid separation by a conventionally known means such as centrifugation or filtration, and the obtained solid is sufficiently washed with water. This is a step of baking at a temperature of 500 ° C. or higher.

  The firing temperature in the step (b) is preferably 500 ° C. or higher, more preferably 500 to 900 ° C., from the viewpoint of removing unreacted alkoxy groups and hydroxyl groups of the titania precursor. By performing the firing treatment in this manner, a clay mineral with titania particle insertion is obtained. The titania particle-inserted clay mineral can be adjusted to a desired particle size by pulverization and classification.

3. Properties of Titania Particle Inserted Clay Mineral In the titania particle inserted clay mineral used in the present invention, the average particle size of the titania particles inserted between the layers is preferably in the range of 3 to 200 nm from the viewpoint of expanding the layers of the clay mineral. The range of 3 to 50 nm is more preferable.
In addition, the said average particle diameter is the value measured by the method shown below.

<Measurement method of average particle size of titania particles in clay mineral containing titania particles>
The titania particle size was measured from an image observed at an acceleration voltage of 200 kv using a scanning transmission electron microscope STEM (Science manufactured by HITACHI). The observation sample was processed by FIB so as to have a thickness of 80 to 100 nm.

Further, the content of titania particles in the titania particle-inserted clay mineral is preferably 10 to 80% by mass, and more preferably 30 to 60% by mass from the viewpoint of uniformly inserting between the clay mineral layers.
In addition, content of the said titania particle | grain is a value obtained by calculating from the quantity of the used layered clay mineral, and the quantity of a hydrolysable titanium compound.

[Friction material forming material]
The friction material of the present invention is formed by using a friction material forming material including a binder resin, the above-mentioned titania particle-inserted clay mineral, a fibrous reinforcing material, a lubricant, a friction modifier, and other fillers, and molding according to a conventional method. ,Obtainable.

  In the material for forming a friction material used in the present invention, it is necessary that the lubricant, the friction modifier, other fillers and the like substantially contain no hard substance having a Mohs hardness of more than 6.

1. Binder Resin The binder resin in the friction material forming material is not particularly limited, and conventionally known thermosetting resins known as binder resins in brake friction materials, such as phenol resins, epoxy resins, polybenzos. Any oxazine resin can be appropriately selected and used.

2. Fibrous Reinforcing Material As the fibrous reinforcing material in the friction material forming material, both organic fibers and inorganic fibers can be used. Examples of organic fibers include high-strength aromatic polyamide fibers (aramid fibers; manufactured by DuPont, trade name “Kevlar”, etc.), flame-resistant acrylic fibers, polyimide fibers, polyacrylate fibers, polyester fibers, and the like. On the other hand, as inorganic fibers, in addition to potassium titanate fibers, basalt fibers, silicon carbide fibers, glass fibers, carbon fibers, wollastonite, etc., ceramic fibers such as alumina silica fibers, stainless fibers, copper fibers, brass fibers, Examples thereof include metal fibers such as nickel fibers and iron fibers. These fibrous substances may be used alone or in combination of two or more.

3. Lubricant, friction modifier, and other fillers The lubricant in the friction material forming material is not particularly limited, and an arbitrary one is appropriately selected from known materials used as lubricants in conventional friction materials. be able to. Specific examples of the lubricant include graphite, fluorinated graphite, carbon black, metal sulfides such as tin sulfide and tungsten disulfide, and polytetrafluoroethylene (PTFE) and boron nitride. These may be used individually by 1 type and may be used in combination of 2 or more type.

  Moreover, there is no restriction | limiting in particular as a friction modifier in the said friction material formation material, Arbitrary things can be suitably selected from the well-known things used as a friction modifier in the conventional friction material. Specific examples of the friction modifier include metal oxides such as magnesia and iron oxide; zirconium silicate; silicon carbide; metal powders such as copper, brass, zinc and iron, and inorganic friction modifiers such as titanate powder. And organic friction modifiers such as rubber dust such as NBR, SBR, and tire tread, and organic dust such as cashew dust. These may be used individually by 1 type and may be used in combination of 2 or more type.

  In the friction material forming material, a swellable clay mineral can be contained as other fillers such as a reinforcing material and a friction modifier. Examples of the swellable clay mineral include kaolin, talc, smectite, vermiculite, and mica.

  Further, calcium carbonate, barium sulfate, calcium hydroxide and the like can be contained.

  In the composite material of the present invention, among the lubricant, friction modifier and other fillers described above, the inorganic filler is treated with an organic compound in order to improve dispersibility in the composite material. Filled fillers can be used.

  Examples of fillers treated with organic compounds include treatment with organic compounds such as swellable clay minerals, calcium carbonate, barium sulfate, magnesia, aluminum powder, copper powder, zinc powder, graphite, tin sulfide, and tungsten disulfide. You can list things.

  The swellable clay mineral has a layered structure, and by treatment with an organic compound, an intercalation compound is formed, the interlaminar is enlarged, delamination is likely to occur, and dispersibility in the composite material of the present invention is improved.

  Examples of the organic compound used for the treatment of the swellable clay mineral include amines and quaternary ammonium salts. Here, as amines, a C1-C18 aliphatic amine, an aromatic amine, etc. can be used, for example. Specific examples of aliphatic amines include diethylamine, amylamine, dodecylamine, stearylamine, didodecylmethylamine hydrochloride and odorate, and specific examples of aromatic amines include aniline, toluidine, xylidine, and phenylene. Examples include diamines. Of these amines, aniline is particularly preferred. On the other hand, preferred examples of the quaternary ammonium salt include dimethyldioctadecylammonium chloride and oleylbis (2-hydroxyethyl) methylammonium chloride.

  Fillers other than the above swellable clay minerals, for example, calcium carbonate, barium sulfate, magnesia, aluminum powder, copper powder, zinc powder, graphite or tin sulfide, treatment with organic compounds such as tungsten disulfide, as organic compounds, It is preferable to use an aliphatic or aromatic primary amine having about 10 to 35 carbon atoms or a silane coupling agent having a primary amine group at the terminal.

  Examples of the aliphatic or aromatic primary amine include n-dodecylamine, n-hexadecylamine, n-octadecylamine, n-nonadecylamine, p-tert-butylaniline, p-octylaniline, p-dodecylaniline and the like. Examples of the silane coupling agent include 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane. Of these, n-dodecylamine is particularly preferred.

  There is no particular limitation on the method of treating the filler with the organic compound, and the organic compound is used as it is in the form of a melt, or the organic compound is dissolved in an appropriate organic solvent, and the solution is treated in a solution. A method or the like can be used.

  There is no particular limitation on the method of incorporating the filler treated with the organic compound in the composite material in this way, and a method of melt kneading together with other components can be used. From the viewpoint of dispersibility, the binder resin It can also be mixed in during the manufacturing process.

[Production of friction material]
In order to produce the friction material of the present invention, the above-mentioned friction material forming material is filled in a mold or the like, preformed at room temperature and a pressure of about 5 to 30 MPa, and then at a temperature of about 130 to 190 ° C. and a pressure of 10 After heating and compression molding for about 5 to 35 minutes under about 100 MPa, heat treatment is performed at a temperature of about 160 to 270 ° C. for about 1 to 10 hours as necessary to produce a desired friction material. Can do.

  The friction material of the present invention thus manufactured maintains a necessary coefficient of friction and suppresses grinding of the mating material during friction braking, and generates a vibration due to deformation of the mating material or a wheel caused by wear powder of the mating material. It is possible to prevent soiling.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Production Example 1
Synthetic fluorine mica (ME-100 manufactured by Co-op Chemical Co., Ltd.), a layered clay mineral, was added to 1000 g of distilled water, an aqueous medium, and stirred for 24 hours at room temperature to swell and disperse. A mica solution was prepared.

  On the other hand, 19 g (0.2 mol) of tetrapropoxytitanium is added to 340 g of an 80% strength by weight acetic acid aqueous solution, and after stirring and mixing at 60 ° C. for 1 hour, the mixture is cooled to 25 ° C. Mix and stir at 25 ° C. for 3 hours.

Next, this mixed solution was subjected to solid-liquid separation by centrifugation to take out a solid content, and then water washing and centrifugation were repeated using distilled water until the pH of the washing solution exceeded 5. Next, the obtained solid content was calcined at 600 ° C. for 72 hours to obtain 15 g of synthetic fluorine mica (hereinafter referred to as TiO ₂ -containing fluorine mica A) in which titania particles were inserted.

The average particle diameter of the titania particles in the TiO ₂ -containing fluorine mica A was about 5 nm as a result of measurement by the method described in the specification, and the content of the titania particles in the TiO ₂ -containing fluorine mica A was 35 It was mass%.

Production Example 2
In Production Example 1, titania particles were inserted between the layers in the same manner as in Production Example 1 except that the amount of tetrapropoxytitanium was changed to 52 g (0.56 mol) and the firing temperature was changed to 800 ° C. 24 g of synthetic mica (hereinafter referred to as TiO ₂ -containing fluorine mica B) was obtained.

The average particle diameter of the titania particles in the TiO ₂ -containing fluorine mica B is about 15 nm as a result of measurement by the method described in the specification, and the content of the titania particles in the TiO ₂ -containing fluorine mica B is 60% by mass.

Examples 1 and 2 and Comparative Examples 1 and 2
A friction material forming material having the composition shown in Table 1 was prepared, and a plate-shaped friction material test piece having a length of 13 mm, a width of 35 mm, and a thickness of 10 mm was produced under the following conditions.

<Friction material test piece production conditions>
Weighed the total composition of Table 1 to 1 kg, mixed using a 10 L Eirich mixer, thermoformed at 150 ° C. for 10 minutes, 30 MPa pressure, and heat treated at 250 ° C. for 3 hours. A friction material plate having a length of 65 mm, a width of 50 mm, and a thickness of 10 mm was produced. This was cut to produce a friction material test piece.

  The friction material test piece was subjected to the following wear test to measure the wear amount of the counterpart material (μm), the friction material wear amount (mm), and the average friction coefficient. The results are shown in Table 1.

<Abrasion test>
Using a wear tester made by Sakai Engineering Co., Ltd., model name "Inertial 1/10 scale tester"
Opponent material: FC250
First braking speed: 100km / h
Braking deceleration: 5.88 m / S ²
Number of braking: 20 times Braking brake temperature 200 ℃, 500 ℃
Under these conditions, the wear amount of the counterpart material (μm), the wear amount of the friction material (mm) and the average friction coefficient were measured.

[note]
1) Phenol resin: Cashew Co., Ltd., trade name “Y-2235”
2) Resin dust: Cashew Co., Ltd., trade name “D-5”
3) Barium sulfate: Mohs hardness 3
4) Dichromium trioxide: Mohs hardness 8
5) Phosphorous graphite: manufactured by Nippon Graphite Industries Co., Ltd., trade name “CD-150”
6) Metal powder: Copper powder, Mohs hardness 3

From Table 1, Example 1 and Example 2 which do not contain dichromium trioxide having a Mohs hardness of about 8 and contain TiO ₂ -containing fluorine mica have a small amount of wear of the counterpart material and have a stable friction coefficient. .

On the other hand, Comparative Example 1 containing dichromium trioxide having a Mohs hardness of about 8 and not containing TiO ₂ -containing fluorine mica has a large amount of wear on the mating material and wear on the friction material. Further, Comparative Example 2 that does not contain dichromium trioxide and TiO ₂ -containing fluorine mica has a large friction material wear amount, transfer to the counterpart material is recognized, and the friction coefficient is also low.

  The friction material of the present invention maintains the necessary coefficient of friction and suppresses the grinding of the mating material during friction braking, preventing the occurrence of vibration due to deformation of the mating material and the contamination of the wheel due to wear powder of the mating material. It is suitable for brake pads for automobiles and the like.

Claims (4)

  A friction material characterized in that it contains substantially no hard substance with a Mohs hardness of more than 6 and contains a layered clay mineral formed by inserting titania particles between layers in a proportion of 0.5 to 20% by mass.   The friction material according to claim 1, wherein the average particle diameter of the titania particles in the layered clay mineral formed by inserting titania particles between the layers is 3 to 200 nm.   The friction material according to claim 1 or 2, wherein the content of titania particles in the layered clay mineral obtained by inserting titania particles between layers is 10 to 80% by mass.   The layered clay mineral formed by inserting titania particles between layers is obtained by calcining a layered clay mineral intercalated with a titania precursor formed by a sol-gel method at a temperature of 500 ° C or higher. The friction material of any one of 1-3.